It is proposed to study various aspects of experimental hypertension and circulatory factors involved in acute renal failure. In the work on hypertension the role of the medulla will be studied in particular. Measurement of inner medullary plasma flow will be carried out and the effects of subcutaneous implantation of medullary fragments and the effects of chemical ablation of the papilla studied, in different experimental models. Spontaneously hypertensive rats will be used for some of the studies. More appropriate experimental models of acute renal failure than are currently available will be developed. Circulatory factors will be studied using the flow probe, in-vivo angiography and renin assays. The effect of pharmacologic agents affecting renin release will be studied to determine the part played by the renin-angiotensin system. BIBLIOGRAPHIC REFERENCES: The renal medulla and mechanisms for hypertension in the spontaneously hypertensive rat. Solez, K., D'Agostini, R. J., Wang, A. L., and Heptinstall, R. H. Fed. Proc. 34:398, 1975 (Abstract). Experimental hypertension. The effects of chemical ablation of the renal papilla on the blood pressure of rats with and without silver-clip hypertension. Heptinstall, R. H., Salyer, D. C., and Salyer, W. C. Am. J. Pathol. 78:297, 1975.